#include <bits/stdc++.h>

using namespace std;

long double f(int l1, int r1, int l2, int r2)
{
	if(l1 == l2 && r1 == r2)
	{
		return (r1 - l1) / 3.0L;
	}
	if(r1 <= l2 || r2 <= l1)
	{
		long double E1 = (l1 + r1) / 2.0L;
		long double E2 = (l2 + r2) / 2.0L;
		return abs(E1 - E2);
	}
	if(l1 <= l2 && l2 <= r1)
	{
		long double aux = f(l2, r1, l2, r2) * (r1 - l2) / (r1 - l1);
		return aux + f(l1, l2, l2, r2) * (l2 - l1) / (r1 - l1);
	}
	if(l1 <= r2 && r2 <= r1)
	{
		long double aux = f(l1, r2, l2, r2) * (r2 - l1) / (r1 - l1);
		return aux + f(r2, r1, l2, r2) * (r1 - l2) / (r1 - l1);
	}
	return f(l2, r2, l1, r1);
}

int main()
{
	ios_base::sync_with_stdio(false), cin.tie(NULL);
	int n, m;
	cin >> n >> m;
	vector<pair<int, int>> a(n), b(m);
	long double tota = 0, totb = 0;
	for(int i = 0; i < n; ++i)
	{
		cin >> a[i].first >> a[i].second;
		tota += (a[i].second - a[i].first);
	}
	for(int i = 0; i < m; ++i)
	{
		cin >> b[i].first >> b[i].second;
		totb += (b[i].second - b[i].first);
	}

	long double ans = 0;
	for(int i = 0; i < n; ++i)
		for(int j = 0; j < m; ++j)
		{
			auto [l1, r1] = a[i];
			auto [l2, r2] = b[j];
			long double prob1 = 1.0L / n;
			long double prob2 = 1.0L / m;
			if(tota)
				prob1 = (r1 - l1) / tota;
			if(totb)
				prob2 = (r2 - l2) / totb;
		
			ans += prob1 * prob2 * f(l1, r1, l2, r2);
		}
	cout << setprecision(20) << fixed << ans << endl;
}